JP4963373B2 - Fuel cell internal state observation device - Google Patents

Description

  The present invention relates to a technique for observing an internal state of a fuel cell.

  2. Description of the Related Art Conventionally, a technique for observing the internal state of a fuel cell has been demanded for various purposes such as fuel cell flow path design evaluation, failure detection, and quality assurance. For example, in a polymer electrolyte fuel cell, the water content of the electrolyte included in the membrane electrode assembly has an important meaning as the internal state quantity of the fuel cell. This is because the output power is significantly reduced according to the decrease in the moisture content of the electrolyte.

JP 2003-77515 A Japanese Patent Laid-Open No. 9-223512 JP 2004-152501 A

  However, a decrease in output power can occur even when the moisture content of the electrolyte is sufficient. Normally, the water generated in the electrolyte is discharged through the gas flow path arranged in the vicinity of the electrolyte, but the flow path is blocked by water due to poor ventilation of the gas flow path. There is. Such a state is called flooding, and the gas does not flow smoothly in the flow path, so that the amount of gas supplied to the electrolyte is reduced and the output power is reduced. When flooding occurs in this way, the output power is reduced despite the high water content of the electrolyte. As described above, in the case where a decrease in output occurs in the polymer electrolyte fuel cell, it is difficult to analyze whether the cause is due to a decrease in the water content of the electrolyte or flooding due to excess water. It was causing problems. This problem was a serious problem because the measures to be dealt with were the opposite of the decrease in the moisture content of the electrolyte and the flooding due to excessive water. Furthermore, such a problem is not limited to the polymer electrolyte fuel cell, but a fuel cell having a loss element that changes in accordance with different internal state quantities such as “activation polarization”, “diffusion polarization”, and “resistance polarization”. It was a common problem.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a technique for observing a distribution state of resistance polarization state quantities in an internal state observation device for observing the internal state of a fuel cell. And

The present invention is an internal state observation device for observing an internal state of a fuel cell having an electrolyte and a plurality of separators sandwiching the electrolyte in order to solve at least a part of the above-described problems,
A plurality of electrodes for conducting electrical connection with a plurality of regions on a plane of one of the plurality of separators by contact at a predetermined contact point of the fuel cell;
A merging portion for merging currents flowing through the plurality of electrodes to have the same potential;
A sensor for measuring an electrode current flowing through each of the plurality of electrodes;
A load unit that is connected to the fuel cell via the merging unit and the other one of the plurality of separators, and controls the load to be variable;
The AC component generated according to the load variation included in each of the measured electrode currents is extracted, and the distribution of state quantities of resistance polarization of the fuel cell is observed based on each of the extracted AC components. An extraction observation unit;
It is characterized by providing.

  In the measuring apparatus according to the present invention, a load unit that controls the load to be variable is connected to the measurement target, and an alternating current component that is generated according to the fluctuation of the load is extracted, and based on each extracted alternating current component Since the distribution of the state quantity of resistance polarization of the fuel cell can be observed, it is possible to estimate the state of the electrolyte by observing the resistance polarization, for example.

In the internal state observation apparatus,
The fuel cell includes a membrane electrode assembly,
The internal state observation device may estimate the water content distribution state of the membrane electrode assembly based on the distribution state of the resistance polarization state quantity observed separately.

  Since the membrane / electrode assembly has an extremely large capacitance by forming an electric double layer capacitance between the electrolyte and the electrode, it has an advantage that the electrolyte resistance can be easily separated from the reaction resistance and can have a remarkable effect. . Furthermore, the estimation of the water content of the electrolyte separated from the channel blockage state is extremely important because the measures (for example, channel design and control operation) to be handled by the channel blockage and the excessive water content of the electrolyte are opposite.

In the internal state observation apparatus,
The extraction observation unit directly measures the output voltage of the fuel cell without passing through the merging unit, and observes the distribution of the state quantity of resistance polarization of the fuel cell in each output state based on the output voltage. You may do it.

  In this way, it is possible to accurately measure the output of the fuel cell by eliminating the resistance caused by the measuring jig including the junction, and it is possible to estimate the internal state according to various output states of the fuel cell. .

In the internal state observing apparatus, a resistance value Rb between contact points that is a resistance value between the predetermined contact points in the fuel cell, and a circuit resistance that is a combined resistance value between the predetermined contact point and the junction. Measure each AC component according to the value Rc and each measured electrode current,
Each of the AC components satisfies the following equation when the maximum value of the current output ratio of the fuel cell assumed between the predetermined contact points is the maximum output ratio Pr and the allowable error is Er. In addition, each electrode current measured by the plurality of electrodes may be regarded as a current output at a contact point where the electrodes are in contact with each other. Here, the allowable error Er> ABS (1 − ((the maximum output ratio Pr + 1) × the circuit resistance value Rc + the resistance value Rb between the contact points) / (2 × the circuit resistance value Rc + the resistance value Rb between the contact points) )). However, the ABS (argument) means a function that returns the absolute value of the argument.

  By so doing, the measurement error due to the leakage current flowing between the plurality of electrodes can be within a presumed allowable range, so that measurement reliability can be improved.

  Such a configuration can be realized by at least one of “increase in resistance value Rb between contact points” and “decrease in circuit resistance value Rc”. “Increase in resistance value Rb between contact points” can be realized by, for example, increasing the resistance value of a measurement object or a measurement jig having contact points or increasing the pitch between contact points. On the other hand, the “decrease in the circuit resistance value Rc” can be realized, for example, by eliminating contact resistance by integrating circuits of a measuring device described later, or by reducing contact resistance by applying liquid metal to the contact surface.

In the measurement device, the circuit resistance value Rc is configured to be equal to or less than one fifth of the resistance value Rb between the contact points,
The measurement device may have a simple configuration in which each electrode current measured by the plurality of electrodes is regarded as a current output at a contact point where each electrode contacts.

  In this way, the measurement error caused by the leakage current flowing between the plurality of electrodes can be set to the general accuracy required in the current density distribution, so that the measurement reliability can be easily increased.

  In the measurement apparatus, the circuit resistance value Rc is a combined resistance of a contact resistance between the predetermined contact point of the measurement target and the electrode and a contact resistance between the electrode and the junction. Therefore, the current density distribution may be measured.

  Since most of the circuit resistance value Rc is occupied by the contact resistance, a simple and practical measuring device can be realized by regarding the sum of the contact resistances as the circuit resistance value Rc.

In the measurement apparatus, the plurality of electrodes and the joining portion are configured as a single unit,
The circuit resistance value Rc may be regarded as a contact resistance between the predetermined contact point and the electrode, and the current density distribution may be measured.

  In this way, the circuit resistance value Rc can be reduced by configuring the electrode and the junction part as one body and eliminating the contact resistance between the electrode and the junction part.

  In the measurement apparatus, the liquid resistance is applied between each of the plurality of electrodes and the measurement target, so that the contact resistance between each of the plurality of electrodes and the measurement target is reduced. You may make it.

  Thus, the circuit resistance value Rc can also be reduced by reducing the contact resistance by applying liquid metal to the contact surface.

  In the measuring apparatus, the liquid metal is preferably an alloy containing gallium and indium. This is because an alloy containing gallium and indium has favorable properties for this purpose in that it has low toxicity and low resistance.

In the measurement apparatus, the measurement object is a battery electrode of a fuel cell provided with a reaction gas flow path,
The distance between each contact surface between each of the plurality of electrodes and the measurement target may be configured to be not more than twice the pitch in the width direction of the reaction gas channel. .

  If it carries out like this, the increase in the contact resistance of a battery electrode and a reactive gas flow path resulting from the nonuniformity of the pressure with respect to a reactive gas flow path may be suppressed.

  In the measurement apparatus, the pitch between the plurality of electrodes is made smaller than the size in the direction perpendicular to the plurality of electrode axes of the sensor by shifting the sensors in the axial direction of the plurality of electrodes. It may be configured as follows.

  In this way, it is possible to increase the density of measurement points while ensuring the sensor size and maintaining the sensing accuracy.

In the measurement apparatus, the measurement object is a battery electrode of a fuel cell provided with a reaction gas flow path,
The plurality of electrodes are:
An electrode rod for guiding current to the junction,
At a predetermined contact point of the measurement object, a contact terminal for contacting with an area larger than a cross-sectional area of the electrode rod;
With
The measuring device may further include a pressure plate that presses each of the contact terminals integrally with the measurement target.

  In this way, the battery electrode suppresses the variation in the contact resistance between the battery electrode and the reaction gas channel and the contact resistance between the collector electrode and the separator caused by the non-uniform pressure on the peak of the reaction gas channel. Can do.

In the above measuring device,
A biasing portion may be provided between the pressure plate and each of the contact terminals.

  By so doing, it is possible to further suppress variation in contact resistance between the battery electrode and the reactive gas flow path, or between the current collecting electrode and the separator, and increase the measurement accuracy.

In the above measuring device,
The plurality of electrodes have a contact surface including a central region capable of conducting by contact and a closed peripheral region surrounding the central region,
The peripheral region may be insulated.

  If it carries out like this, resistance value Rb between contact points can be increased, making a contact point space | interval small.

  The present invention can be realized in a current density distribution measuring method, a fuel cell control device equipped with the internal state observation device, a fuel cell system, and other various aspects.

Hereinafter, embodiments of the present invention will be described in the following order based on examples.
A. Configuration of internal state observation apparatus in the first embodiment of the present invention:
B. State observation in the first embodiment of the present invention:
C. State observation in the second embodiment of the present invention:
D. Variations:

A. Configuration of internal state observation apparatus in the first embodiment of the present invention:
FIG. 1 is a schematic configuration diagram of an internal state observation device 100 and an observation target in the first embodiment of the present invention. The internal state observation device 100 includes a plurality of measurement electrodes 120, a current collecting plate 111, an end plate 109 and a terminal plate 107 as measurement jigs, an electronic load device 110, and a power density distribution measurement device 210. ing. In the present embodiment, the internal state observation apparatus 100 has the fuel cell 201 as an observation target.

  In this embodiment, the fuel cell 201 is a polymer electrolyte fuel cell including a membrane electrode assembly 202 and two separators 203 and 204 made of carbon that sandwich the membrane electrode assembly 202 from both sides. The two separators 203 and 204 are formed with gas flow paths (not shown) through which the reaction gas flows on the membrane electrode assembly 202 side. The fuel battery cell 201 generates electric power by the reaction of the reaction gas and outputs it to the outside through the two separators 203 and 204.

  The electronic load device 110 is configured to be able to vary the load periodically at a variable frequency. The electronic load device 110 is electrically connected between the current collecting plate 111 and the terminal plate 107. The power density distribution measuring apparatus 210 measures the power density distribution based on the potential difference between the two separators 203 and 204 and the current flowing through each of the measurement electrodes 120. The current flowing through each measurement electrode 120 is measured according to the output of the current sensor 126 provided in each measurement electrode 120.

  In this embodiment, the water content (or water content distribution) in each part of the electrolyte (not shown) included in the membrane electrode assembly 202 sandwiched between the two separators 203 and 204 is estimated based on the power density distribution. Details of the measurement method will be described later. The measurement is based on the power density distribution in order to estimate the water content distribution in each power output state, and the water content distribution may be estimated directly from the current density distribution.

  FIG. 2 is an enlarged view of a plurality of measurement electrodes 120 that measure the current value output from each portion of the separator 204. Each of the measurement electrodes 120 includes a rod 128, two current collecting electrodes 124 and 125 connected to both ends of the rod 128, and a current sensor 126.

  In this embodiment, the current sensor 126 is a sensor using a Hall element that can measure a change in magnetic field with high sensitivity. The current sensor 126 outputs an electrical signal corresponding to a magnetic field that changes according to the current flowing through the rod 128.

  FIG. 3 is an explanatory view showing an arrangement state of the collecting electrodes 125 on the separator 204 in the first embodiment of the present invention. In this embodiment, the interval between the collecting electrodes 125 is set to 3 mm. Such a setting is preferably set so that the interval between the collecting electrodes 125 is not more than twice the pitch in the width direction of the flow path formed in the separator 204. This is because the pressing pressure by the plurality of collecting electrodes 125 is uniformly transmitted to each flow path.

  FIG. 4 shows an equivalent circuit of an electric circuit composed of the internal state observation device 100 and the fuel cell 201 to be observed. This equivalent circuit includes a fuel cell 201 that generates electric power, a resistor Rb, a contact resistor Rc1, a wiring resistor Rc2, and an electronic load device 110. The resistance Rb is a resistance inside the separator 204 between the adjacent collector electrodes 125. The contact resistance Rc1 is a contact resistance generated due to the contact between the current collecting electrode 125 and the separator 204. The wiring resistance Rc2 is the wiring resistance of the entire internal state observation apparatus 100.

  FIG. 5 is an explanatory diagram showing a part of the equivalent circuit extracted for easy understanding. As described above, in this embodiment, the current value output from each part of the separator 204 is measured in order to estimate the reaction state of the reaction gas in each part Fc1 and Fc2 of the membrane electrode assembly 202. Such measurement is performed by measuring the value of the current flowing through the measurement electrode 120. Specifically, the current values i1 and i2 output by the potentials v1 and v2 generated at the respective portions of the separator 204 are obtained by measuring the current values i3 and i4 flowing through the two measurement electrodes 120. It is measured.

  However, the current values i1 and i2 are not simply proportional to the current values i3 and i4, respectively. This is because the current flows also inside the separator 204, so that the current leaks from the portion where the potential v2 is generated to the measurement electrode 120 side where the current value i3 flows. A measurement method that takes into account the quantitative analysis of such leakage will be described later.

  FIG. 6 is an explanatory diagram showing an example of an equivalent circuit of a part Fc1 of the fuel cell 201 to be observed. This equivalent circuit is composed of a single parallel circuit composed of a reaction resistor Rdif1 and an electric double layer capacitor Cd1 and an electrolyte resistor Rsol1 connected in series to the parallel circuit for easy understanding. It is supposed to be. Here, “reaction resistance Rdif1” represents a loss caused by supply or drainage of the reaction gas to the membrane electrode assembly 202. “Electric double layer capacitance Cd1” represents a loss due to the activation polarization of the membrane electrode assembly 202. “Electrolyte resistance Rsol1” is the reciprocal of the conductivity of the electrolyte (not shown) included in the membrane electrode assembly 202. It is known that this conductivity depends significantly on the water content of this electrolyte. In the examples described below, the moisture content of the electrolyte is estimated based on this dependency.

B. State observation in the first embodiment of the present invention:
In this embodiment, the electrolyte resistance Rsol1 is measured in order to estimate the moisture content distribution in each part of the electrolyte. The electrolyte resistance Rsol1 is measured by separating the reaction resistance Rdif1 from the measurable resistance value (the internal resistance of a part Fc1 of the fuel cell 201). The reaction resistance Rdif1 is separated, for example, by changing the load of the electronic load device 110 at a sufficiently short predetermined period (that is, a predetermined high frequency), and the value of the current flowing through the measuring electrode 120 by a band-pass filter adjusted to the predetermined period This is done by extracting the AC component from. This extraction process is performed by the power density distribution measuring apparatus 210.

  The reason why such separation is possible is that the AC component of the output current of the fuel cell flows through the electric double layer capacitance Cd1 having a low impedance at a high frequency instead of the reaction resistance Rdif1 if the frequency is high. This is because the internal resistance of a part Fc1 of the battery cell 201 approaches the electrolyte resistance Rsol1. In particular, the membrane electrode assembly 202 is suitable because it constitutes an electric double layer capacitance and has a very large capacitance in Farad units. As the frequency of the variable load increases, the electric double layer capacitance Cd1 flows with less impedance as the frequency increases. However, if the frequency is excessively high, the influence of the circuit of the internal state observation device 100 and the inductance component of the observation target occurs. It is preferable to determine this as a trade-off with a large inductance component.

  Furthermore, in the present embodiment, the power density distribution measuring apparatus 210 further measures the power density distribution using the potential difference between the two separators 203 and 204, so that various fuel cell cells 201 to be observed The moisture content distribution in the output state can be estimated.

  As described above, the first embodiment observes the water content distribution state of the electrolyte (not shown) of the membrane electrode assembly 202 based on the distribution (or AC current component) of the AC power component included in the output power of the fuel cell 201. can do.

C. State observation in the second embodiment of the present invention:
The second embodiment of the present invention is different from the first embodiment in that the influence of the leakage current inside the separator 204 is suppressed based on the following analysis from the alternating current density distribution.

The circuit equation of the equivalent circuit of FIG. 5 is as follows. Here, in order to make the circuit equation easy to understand, assuming that the combined resistance of the contact resistance Rc1 and the wiring resistance Rc2 is the circuit resistance Rc and v2> v1, the following expression is derived by Kirchhoff's law.
(1) First formula: i1 + i2 = i3 + i4
(2) Second formula: i3 = i1 + i5
(3) Third formula: i4 = i2-i5

Further, when attention is paid to the potential of each part, the following expression is derived.
(1) Fourth formula: v1 = v2−Rb × i5
(2) Formula 5: v0 = v1-Rc × i3
(3) Sixth formula: v0 = v2-Rc × i4

When the simultaneous equations of the first to sixth formulas are solved, the following formula is derived.
(1) Formula 7: i1 = i3 + Rc / Rb (i3-i4)
(2) Eighth Formula: i2 = i4 + Rc / Rb (−i3 + i4)
Here, the currents i1 and i2 are currents to be measured, and the currents i3 and i4 are currents measured by the current sensor 126. The second term of the seventh and eighth equations corresponds to the current leaking inside the separator 204.

  The measurement method of the second embodiment has high practicality realized by the inventor paying attention to the fact that the second term of the seventh and eighth equations can be adjusted by the hardware configuration of the internal state observation device 100. This is a measurement method. According to this method, there is an advantage that the measurement error caused by the leakage current flowing between the plurality of electrodes can be within the allowable range assumed in advance with a simple configuration.

For example, when the allowable error Er is defined as current value i5 / current value i2 (FIG. 5) and the maximum value of the current output ratio at each measurement point is assumed to be the maximum output ratio Pr, the first to sixth expressions It can be understood that the hardware of the internal state observation device 100 may be configured to satisfy the following ninth equation by solving the simultaneous equations.
Ninth equation: allowable error Er> ABS (1 − ((maximum output ratio Pr + 1) × circuit resistance value Rc + contact point resistance value Rb) / (2 × circuit resistance value Rc + contact point resistance value Rb)). However, ABS (argument) means a function that returns the absolute value of the argument.

  Such a hardware configuration can be realized by at least one of “increasing resistance value Rb between contact points” and “decreasing circuit resistance value Rc”. “Increase in resistance value Rb between contact points” can be realized by, for example, increasing the resistance value of a measurement object or a measurement jig having contact points or increasing the pitch between contact points. On the other hand, the “decrease in the circuit resistance value Rc” can be realized, for example, by eliminating contact resistance by integrating circuits of a measuring device described later, or by reducing contact resistance by applying liquid metal to the contact surface.

  Specifically, the “decrease in the circuit resistance value Rc” can be reduced by applying a predetermined metal between the current collecting electrode 125 and the separator 204. Examples of metals that can be applied include ductile metals such as indium and lead, and liquid metals such as gallium-indium alloys, mercury, and sodium. From the viewpoint of reducing contact resistance, a liquid metal is preferable, and from the viewpoint of safety, an alloy containing gallium and indium such as a gallium-indium alloy is preferable. The “decrease in the circuit resistance value Rc” means that the plurality of measurement electrodes 120 and the current collecting plate 111 are integrated to form an integrated measurement electrode 120a (FIG. 7), and the contact resistance between them. The circuit resistance value Rc can also be reduced by eliminating.

  For example, the circuit resistance value Rc is measured by the contact resistance between the collecting electrode 125 and the separator 204 and the contact between the measuring electrode 120 and the current collecting plate 111. You may make it consider that it is the combined resistance of resistance. This is because most of the circuit resistance value Rc is occupied by the contact resistance. However, when the measurement electrode 120 and the current collecting plate 111 are integrally configured, the circuit resistance value Rc can be regarded as a contact resistance between the current collecting electrode 125 and the separator 204.

  On the other hand, the “increase in the resistance value Rb between contact points” is a method of using a separator 204 having a large resistance material or a plate having a large resistance value such as a carbon plate between the separator 204 and the collector electrode 125 as a measurement jig. And a configuration in a fourth modification described later can be realized.

  Furthermore, as a simple configuration, if the hardware is configured so that the circuit resistance value Rc is 1/5 or less of the inter-contact point resistance value Rb, current density distribution measurement can generally be performed with sufficient accuracy. The inventor has derived this from many actual measurement examples.

  As described above, in the second embodiment, since the leakage current can be reduced by the hardware configuration of the internal state observation device 100, the measurement error due to the leakage current can be suppressed and the current density distribution can be easily measured. There is an advantage that can be.

D. Variations:
As mentioned above, although several embodiment of this invention was described, this invention is not limited to such embodiment at all, and implementation in various aspects is possible within the range which does not deviate from the summary. It is. For example, the following modifications are possible.

D-1. In the above embodiment, the current sensor 126 is disposed at the same position in the axial direction of the measurement electrode 120. For example, the current sensor 126 is shifted in the axial direction of the measurement electrode 120 as shown in FIG. Accordingly, the pitch of the measurement electrodes 120 may be configured to be smaller than the size of the current sensor 126 in the direction perpendicular to the measurement electrodes 120. In this way, it is possible to increase the density of measurement points while ensuring the sensor size and maintaining the sensing accuracy.

D-2. In the above embodiment, the current collecting plate 111 presses the plurality of measurement electrodes 120 against the fuel cell 201 (FIG. 1) as the measurement object. For example, as shown in FIG. May be provided with a pressure plate 130 that is pressed against the object to be measured. By so doing, it is possible to suppress variations in the pressing pressure for each measuring electrode 120 caused by manufacturing tolerances of the lengths of the plurality of measuring electrodes 120.

  Note that the pressure plate 130 only needs to be configured to have sufficiently higher rigidity in the surface pressure direction than the current collecting plate 111a. When the pressure plate 130 is formed of a conductor, the pressure plate 130 is provided between the current collecting electrodes 125. In order to prevent a short circuit, an insulator 130n may be provided between the collector electrode 125 and the collector electrode 125.

  Further, for example, as shown in FIG. 10, a spring 125 s for biasing may be provided between the pressure plate 130 and the current collecting electrode 125. By so doing, it is possible to further suppress variation in contact resistance between the battery electrode and the reaction gas flow path, and to improve measurement accuracy.

D-3. In the above embodiment, the front surface of the contact surface of the current collecting electrode 125 is configured to be conductive, but may be configured as shown in FIG. 11, for example. FIG. 11 is an explanatory view showing a contact surface of the collecting electrode 125. The contact surface has an insulating region 125n (hatched region) provided with an enamel coating for insulation and a conductive region 125c capable of conducting. Liquid metal is applied to the conduction region 125c. The insulating region 125n is configured as a closed region surrounding the conductive region 125c.

  In this configuration, since the leakage current of the path as shown in FIG. 12 can be prevented, the contact point resistance as shown in FIG. 13 is reduced while the contact point interval is made small in order to equalize the pressing pressure. The value Rb can be increased.

D-4. In the above embodiment, the power density distribution output from one cell of the fuel cell 201 is measured from one side. For example, as shown in FIG. 14, the measurement electrode 120 is sandwiched between the fuel cell stacks. You may do it. Note that the present invention can be realized in an internal state observation method, a device such as a fuel cell equipped with the internal state observation device, and other various aspects.

D-5. In the above embodiment, the moisture content of the electrolyte of the polymer electrolyte fuel cell is estimated, but not limited to the polymer electrolyte fuel cell, such as “activation polarization”, “diffusion polarization”, “resistance polarization”, etc. Applies to fuel cells with loss factors that vary according to different internal state parameters, separating the distribution of resistance polarization state quantities of fuel cells from other losses (eg, “activation polarization” and “diffusion polarization”) Can be observed.

  In general, the present invention extracts an alternating current component generated in accordance with a load variation included in each electrode current, and represents a physical quantity (that is, a state quantity) representing a state of resistance polarization of the fuel cell based on each extracted alternating current component. ) Distribution may be observed. However, the polymer electrolyte fuel cell has an extremely large electrostatic capacity by forming an electric double layer capacity between the electrolyte and the electrode, and it is very important to estimate the water content and the clogged state. Since the measures to be taken are the opposite, it has a remarkable effect.

  In general, a fuel cell includes a capacitance representing “activation polarization”, a resistance representing “diffusion polarization”, and a resistance representing “resistance polarization”, and a plurality of parallel circuits of capacitance / resistance are provided. It is composed of a circuit connected in series and a resistor connected in series to this circuit. In this case as well, the “resistance polarization” can be separated from the “diffusion polarization” by using a variable load as described above. Here, the “activation polarization” is a loss due to the fact that the electrode of the fuel cell needs energy for activation. “Resistance polarization” is a loss caused by electrolyte resistance, resistance between the electrolyte resistance and the electrode, or the like. “Diffusion polarization” is loss due to supply of reactants to the electrolyte, removal of products from the electrolyte, and the like.

  Further, “observing” in the claims has a broad meaning and includes obtaining a measured value (for example, current density distribution) having a strong correlation with the state quantity of resistance polarization of the fuel cell.

1 is a schematic configuration diagram of an internal state observation device 100 and an observation target in a first embodiment of the present invention. The enlarged view of the several electrode 120 for a measurement which measures the electric current value output from each part of the separator 204. FIG. Explanatory drawing which shows the array state on the separator 204 of the current collection electrode 125 in 1st Example of this invention. Explanatory drawing which shows the equivalent circuit of the electric circuit comprised by the internal state observation apparatus 100 and the fuel cell 201 of observation object. Explanatory drawing which shows a part of equivalent circuit of the electric circuit comprised by the internal state observation apparatus 100 and the fuel cell 201 of observation object. Explanatory drawing which shows an example of the equivalent circuit of some FC1 of the fuel cell 201 of observation object. Explanatory drawing which shows the integrated measurement electrode 120a by which the current collection board 111 was integrated with the several electrode 120 for measurement. Explanatory drawing which shows the some electrode 120 for a measurement in a 1st modification. The schematic block diagram of the internal state observation apparatus 100 and observation object in the 2nd modification. The schematic block diagram of the internal state observation apparatus 100 and observation object in a 3rd modification. The internal state observation apparatus 100 in the 4th modification and the schematic block diagram of observation object. Explanatory drawing which shows the leakage current suppressed by the 4th modification. Explanatory drawing which shows a mode that the leakage current was suppressed in the 4th modification. The internal state observation apparatus 100 in a 5th modification and the schematic block diagram of an observation object.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Internal state observation apparatus 107 ... Terminal plate 109 ... End plate 110 ... Electronic load apparatus 111, 111a ... Current collecting plate 120, 120a ... Measuring electrode 120 ... Measuring electrode 124, 125 ... Current collecting electrode 126 ... Current sensor 128 DESCRIPTION OF SYMBOLS ... Rod 130 ... Pressure plate 201 ... Fuel cell 202 ... Membrane electrode assembly 203 ... Separator 204 ... Separator 210 ... Power density distribution measuring device

Claims (14)

An internal state observation device for observing an internal state of a fuel cell having an electrolyte and a plurality of separators sandwiching the electrolyte,
A plurality of electrodes for conducting electrical connection with a plurality of regions on a plane of one of the plurality of separators by contact at a predetermined contact point of the fuel cell;
A merging portion for merging currents flowing through the plurality of electrodes to have the same potential;
A sensor for measuring an electrode current flowing through each of the plurality of electrodes;
A load unit that is connected to the fuel cell via the merging unit and the other one of the plurality of separators, and controls the load to be variable periodically at a variable frequency ;
The AC component generated according to the load variation included in each of the measured electrode currents is extracted, and the distribution of state quantities of resistance polarization of the fuel cell is observed based on each of the extracted AC components. An extraction observation unit;
Equipped with a,
The extraction observation unit is
Each electrode current measured by the plurality of electrodes is configured to be regarded as a current output at a contact point where each electrode contacts,
The resistance value Rb between contact points, which is a resistance value between the predetermined contact points in the fuel cell, and the circuit resistance value Rc, which is a combined resistance value between the predetermined contact point and the junction, are measured. And measuring each of the alternating current components according to each electrode current,
The resistance between the predetermined contact points and the combined resistance between the predetermined contact points and the junction are the maximum output of the current output ratio of the fuel cell assumed between the predetermined contact points. and the ratio Pr, when the error allowed and Er, characterized that you have been configured so as to satisfy the following equation, the internal state observer.
The allowable error Er> ABS (1 − ((the maximum output ratio Pr + 1) × the circuit resistance value Rc + the resistance value Rb between the contact points) / (2 × the circuit resistance value Rc + the resistance value between the contact points Rb))
However, the ABS (argument) means a function that returns the absolute value of the argument. The internal state observation device according to claim 1,
The fuel cell includes a membrane electrode assembly,
The said extraction observation part is an internal state observation apparatus which estimates the moisture content distribution state of the said membrane electrode assembly based on the distribution state of the observed state quantity of resistance polarization. The internal state observation device according to claim 1 or 2,
The extraction observation unit directly measures the output voltage of the fuel cell without passing through the merging unit, and observes the distribution of the state quantity of resistance polarization of the fuel cell in each output state based on the output voltage. , An internal state observation device. The internal state observation device according to claim 1 ,
The circuit resistance value Rc is configured to be 1/5 or less of the resistance value Rb between the contact points,
The internal state observation device is configured to regard each electrode current measured by the plurality of electrodes as a current output at a contact point where the electrodes are in contact with each other. It is an internal state observation apparatus of Claim 1 thru | or 4 , Comprising:
The circuit resistance value Rc is regarded as a combined resistance of a contact resistance between a predetermined contact point of the fuel cell and the electrode and a contact resistance between the electrode and the junction, and the current An internal state observation device that measures density distribution. The internal state observation device according to any one of claims 1 to 5 ,
The plurality of electrodes and the merging portion are configured as a single unit,
The internal state observation device that measures the current density distribution by regarding the circuit resistance value Rc as a contact resistance between a predetermined contact point of the fuel cell and the electrode. The internal state observation device according to any one of claims 1 to 6 ,
An internal state in which a contact resistance between each of the plurality of electrodes and the fuel cell is reduced by applying a liquid metal between each of the plurality of electrodes and the fuel cell. Observation device. The internal state observation device according to claim 7 ,
The internal state observation device, wherein the liquid metal is an alloy containing gallium and indium. The internal state observation device according to any one of claims 1 to 8 ,
The fuel cell is a battery electrode of a fuel cell having a reaction gas flow path,
An internal state observation device configured such that a distance between each contact surface between each of the plurality of electrodes and the fuel cell is not more than twice a pitch in a width direction of the reaction gas flow path. . The internal state observation device according to any one of claims 1 to 9 ,
By shifting the sensor relative to each other in the axial direction of the plurality of electrodes, the pitch between the plurality of electrodes is configured to be smaller than the size in the direction perpendicular to the flow direction of the plurality of electrodes of the sensor. An internal state observation device. It is an internal state observation apparatus in any one of Claims 1 thru | or 10 , Comprising:
The fuel cell is a battery electrode of a fuel cell having a reaction gas flow path,
The plurality of electrodes are:
An electrode rod for guiding current to the junction,
At a predetermined contact point of the fuel cell, a contact terminal for contacting in a larger area than a cross-sectional area of the electrode rod;
With
The extraction observation unit further includes a pressure plate that presses each of the contact terminals against the fuel cell as a unit. The internal state observation device according to claim 11 , further comprising:
An internal state observation device comprising an urging portion between each of the pressure plate and the contact terminal. The internal state observation device according to any one of claims 1 to 12 , further comprising:
The plurality of electrodes have a contact surface including a central region capable of conducting by contact and a closed peripheral region surrounding the central region,
The peripheral region is an internal state observation device that is insulated. A state observation method for observing an internal state of a fuel cell having an electrolyte and a plurality of separators sandwiching the electrolyte,
At a predetermined contact point of the fuel cell, a plurality of electrodes that are electrically connected to a plurality of regions on a plane included in one of the plurality of separators by contact, and currents flowing through the plurality of electrodes are merged to have the same potential. A step of preparing a junction to be
Measuring an electrode current flowing through each of the plurality of electrodes;
Connected to the fuel cell via the merging portion and the other one of the plurality of separators, and controlling the load to be variable periodically at a variable frequency ; and
The AC component generated according to the load variation included in each of the measured electrode currents is extracted, and the distribution of state quantities of resistance polarization of the fuel cell is observed based on each of the extracted AC components. Process,
Equipped with a,
The step of observing the distribution of the fuel cell comprises:
Each electrode current measured by the plurality of electrodes is configured to be regarded as a current output at a contact point where each electrode contacts,
The resistance value Rb between contact points, which is a resistance value between the predetermined contact points in the fuel cell, and the circuit resistance value Rc, which is a combined resistance value between the predetermined contact point and the junction, are measured. Measuring each alternating current component in response to each electrode current,
The resistance between the predetermined contact points and the combined resistance between the predetermined contact points and the junction are the maximum output of the current output ratio of the fuel cell assumed between the predetermined contact points. and the ratio Pr, when the error allowed and Er, characterized that you have been configured so as to satisfy the following equation, the state observation method.
The allowable error Er> ABS (1 − ((the maximum output ratio Pr + 1) × the circuit resistance value Rc + the resistance value Rb between the contact points) / (2 × the circuit resistance value Rc + the resistance value between the contact points Rb))
However, the ABS (argument) means a function that returns the absolute value of the argument.

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